The purpose of this project is to determine the specificity and plasticity by which neurons regulate the development, maintenance or regeneration of traget tissue. In one study, neurons in grafts of sensory ganglia were isolated in the anterior chamber of the eye for one year at which time tongue grafts were added. The isolated neurons responded to the tongue tissue by growing axons into it where they induced taste bud formation. In another study, it was shown that the rejection of neurons in rat sensory ganglia could be prevented by treatment with the immunosuppressive agent Cyclosporin-A and that these surviving neurons could regenerate axons into tongue tissue and induce the formation of taste buds. Cyclosporin-A was also found capable of preventing the rejection of muscle allografts which ultimately became reinnervated by host axons. Muscle in a rat with congenital absence of the peroneal nerve was reinnervated by another nerve to see if muscle spindles (stretch recepotrs) would appear. No spindles were found indicating that if innervation is missing during a critical period of embryonic muscle development spindle receptors do not form.